Nonvolatile memory devices are a commonly used electronic component that can store information as data in a plurality of memory cells, the information remaining stored in the memory cells when electrical power to the memory devices is terminated. Flash memory devices are nonvolatile memory devices which can store information in the memory cells through conventional programming and erase techniques.
Some flash memory devices have multi-bit memory cells which can store more than one bit per memory cell. For example, a conventional semiconductor/oxide-nitride-oxide on semiconductor (SONOS) type memory device is capable of storing two bits of data in one memory cell. One typical programming technique of such SONOS memory devices is hot electron injection which involves applying appropriate voltage potentials to the gate source and drain of the device for a specified duration until a charge storing layer accumulates charge. While hot electron injection is a reliable programming technique, it requires high voltage potentials and a relatively high programming current. The high voltage potentials are produced by charge pumps which consume space within the memory devices. The relatively high programming current also restricts the number of memory cells that can be programmed simultaneously.
Accordingly, there is a need for multi-bit flash memory devices which require lower voltage potentials and lower current for programming. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.